Linear protection method of the optical network

ABSTRACT

The present invention discloses a linear protection method for an optical network, used for protecting a failed service path in the optical network, and the method comprises: setting priorities of services carried on service paths participating in linear protection of the optical network as service priorities; selecting, from the service paths participating in the linear protection, a service path of which the service priority is lower than that of the failed service path as a protection path, and bridge switching the service on the failed service path to the protection path. The present invention implements protection of service paths according to the priority of the service carried on the failed service path, and enhances the security of service paths.

CROSS REFERENCE RELATED APPLICATIONS

This application is a national phase of PCT/CN2007/003837 filed Dec. 27,2007, which claims priority to China Application Serial No.200710124710.5, filed Nov. 15, 2007, both of which are entirelyincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to the field of service path protection inan optical network, and in particular, to a linear protection method foran optical network.

BACKGROUND OF THE INVENTION

Currently, standards relevant with SDH (Synchronous Digital Hierarchy)and OTN (Optical Transmission Net) all define the 1:N linear protectionmechanism, and standards relevant with OTN also refer to a M:Nprotection method for a communication network. However, the protectionmechanisms in the prior art have the following drawbacks:

1. The numbers of working paths and protection paths are required to befixedly configured. If the number of protection paths configured is lessthan that of the working paths, part of the working path services maynot be protected when many working paths break down simultaneously.

2. When executing extra services, the protection paths do notdifferentiate the priority of the extra services, causing low securityof the extra services.

The protection configuration manner in an optical network in the priorart is not sufficiently flexible, and the security of services should befurther enhanced. Therefore, the prior art needs to be improved anddeveloped.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is toprovide a linear protection method for an optical network, so that afailed service path in an optical network can be flexibly protectedaccording to the priority of its service.

In order to solve the above problem, the present invention provides alinear protection method for an optical network, used for protecting afailed service path in the optical network, the method comprising thefollowing steps of:

A. setting priorities of services carried on service paths participatingin linear protection of the optical network as service priorities; and

B. selecting, from the service paths participating in the linearprotection, a service path of which the service priority is lower thanthat of the failed service path as a protection path, and bridgeswitching the service on the failed service path to the protection path.

Furthermore, the method also comprises the following step before thestep B:

configuring fixed priorities for the service paths participating in thelinear protection of the optical network and setting the servicepriorities of the service paths to be equal to the fixed priorities.

Furthermore, the method also comprises:

setting a node where the failed service path is located in the opticalnetwork as a failure point, which selects the protection path for thefailed service path in the step B.

Furthermore, the step B comprises:

selecting, from the service paths participating in the linearprotection, a service path, of which the service priority is lower thanthat of the failed service path and meanwhile is the lowest, as theprotection path, bridge switching the service on the failed service pathto the protection path, and modifying the service priority of theprotection path to be the service priority of the failed service path.

Furthermore, the method also comprises:

if the service path, of which the service priority is lower than that ofthe failed service path and meanwhile is the lowest, is already aprotection path, then revoking existing service bridge switching on theprotection path, and then bridge switching the service on the failedservice path to the protection path.

Furthermore, the method also comprises:

if there are a plurality of service paths of which the servicepriorities are lower than that of the failed service path and meanwhileare the lowest, then selecting therefrom a service path which is anon-protection path as the protection path of the failed service path.

Furthermore, the method also comprises:

if there are a plurality of service paths of which the servicepriorities are lower than that of the failed service path and meanwhileare the lowest, but all of the plurality of service paths are alreadyprotection paths, then selecting therefrom a protection path with thelowest fixed priority as the protection path of the failed service path.

Furthermore, the step B further comprises a process of restoring thefailed service path, which comprises the following steps of:

C1. revoking existing service bridge switching on the protection pathcorresponding to the failed service path, and restoring the servicecarried on the protection path; and

C2. restoring a protection priority of the protection path correspondingto the failed service path to the service priority thereof.

Furthermore, the method also comprises the following step after the stepC2:

the failure point detecting whether there are other failed service pathsfor which service bridge switching is not performed yet, if yes, findingout a service path with the highest service priority therefrom in orderto protect the failed service path with the highest service priority.

Furthermore, the step B further comprises a process of protection pathadjustment, which comprises the following steps of

D1. selecting a protection path with the highest fixed priority;

D2. selecting a non-protection path with the lowest service priority;

D3. comparing the fixed priority of the protection path with the servicepriority of the non-protection path; if the former one is higher thanthe latter one, revoking the service bridge switching on the protectionpath with the highest fixed priority, restoring the service priority ofthe protection path with the highest fixed priority to the fixedpriority thereof, and using the non-protection path with the lowestservice priority as a new protection path; and

D4. setting up the service bridge switching previously on the protectionpath with the highest fixed priority on the non-protection path with thelowest service priority, and modifying the service priority of thenon-protection path with the lowest service priority to be the servicepriority of the protection path with the highest fixed priority.

Compared with the prior art, the present invention provides a linearprotection method for an optical network, in which when a service pathhas a failure, a service path of which the service priority is lowerthan that of the failed service path is selected as a protection path,and the service on the failed service path is bridge switched to theselected protection path; thereby implementing protection of servicepaths according to the priority of the service carried on the failedservice path, and enhancing the security of the service paths.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an initial state when none of the seven service paths in aSDH network has a failure according to the present invention;

FIG. 2 shows a process of bridge switching the service on the secondservice path having a failure to the seventh service path among theseven service paths in the SDH network according to the presentinvention;

FIG. 3 shows an initial state before revoking service bridge switchingamong the seven service paths in the SDH network according to thepresent invention;

FIG. 4 shows the state after revoking the service bridge switching fromthe second service path to the sixth service path among the sevenservice paths in the SDH network according to the present invention;

FIG. 5 shows the final state after revoking service bridge switchingamong the seven service paths in the SDH network according to thepresent invention;

FIG. 6 shows an initial state before protection path adjustment amongthe seven service paths in the SDH network according to the presentinvention;

FIG. 7 shows the state after revoking the fifth service path to use as aprotection path in protection path adjustment among the seven servicepaths in the SDH network according to the present invention;

FIG. 8 shows the final state after protection path adjustment among theseven service paths in the SDH network according to the presentinvention.

PREFERRED EMBODIMENTS OF THE INVENTION

Preferred embodiments of the present invention will be further describedin detail below with reference to the drawings.

In the linear protection method for an optical network provided by thepresent invention, a detected failure node on a service path is regardedas a failure point; the node of the other end corresponding to thefailure point and located in the same linear protection of the opticalnetwork is regarded as a distal end of the failure point.

The present invention firstly assigns a fixed priority to each servicepath in the linear protection of the optical network, the priority ofthe service carried on the service path is service priority, and thefixed priority of the service path is set to be equal to the servicepriority before service bridge switching is performed between servicepaths. The protection of the failed service path in the presentinvention is carried out according to the service priorities of theservice paths, instead of using the method of dividing the service pathsinto working paths and protection paths as used in the prior art,thereby increasing security and effectiveness of the linear protectionof the optical network.

The process of selecting a protection path for a failed service path andbridge switching the service on the failed service path to theprotection path according to the present invention comprises thefollowing steps of:

101, the failure point seeking a service path having the lowest servicepriority from service paths with service priorities lower than that ofthe failed service path as a protection path; and if no service pathsatisfying such condition is found, proceeding to step 105;

If a service path satisfying the condition is found and the service pathis not used as a protection path yet, then proceeding to step 103;wherein, if a plurality of service paths, of which the servicepriorities are lower than that of the failed service path and are alsothe lowest service priority, are found, then selecting one service pathbeing a non-protection path therefrom as the protection path of thefailed service path, and proceeding to step 103;

If a service path satisfying the condition is found, but the servicepath is already a protection path, then proceeding to step 102; wherein,if the found plurality of service paths, of which the service prioritiesare lower than that of the failed service path and are also the lowestservice priority, are all protection paths already, then selecting aprotection path having the lowest fixed priority therefrom as theprotection path of the failed service path, and proceeding to step 102;

Wherein, apparently the protection path to be found is a service paththat has no failure currently.

102, transmitting a protocol message in the protection path according tothe service bridge switching flow of 1:N or M:N protection protocol inthe prior art, the process of transmitting the protocol message beingconsistent with the 1:N linear protection protocol defined in the SDH orOTN standard, and by the transmission of the protocol message,conforming that the protection path can be used for protection of thefailed service path, then revoking the existing service bridge switchingon the protection path, afterwards, the failure point and the distal endof the failure point bridge switching the service on the failed servicepath to the protection path, then proceeding to step 104.

The service bridge switching flow according to the 1:N or M:N protectionprotocol in the prior art and the process of transmitting the protocolmessage in the present invention is consistent with the prior art, andwill not be repeated here.

103, transmitting a protocol message in the protection path according tothe protection switching flow of 1:N or M:N protection protocol in theprior art, confirming by the transmission of the protocol message thatthe protection path can be used for protection of the failed servicepath, and then the failure point and the distal end of the failure pointbridge switching the service on the failed service path to theprotection path.

104, modifying the service priority of the protection path to be theservice priority of the failed service path at the failure point and thedistal end of the failure point.

105, end.

According to a second preferred embodiment of the present invention,when the failed service path in the first preferred embodiment isrestored, a process of restoring the service carried on the failedservice path added by the present invention is as follows:

201, revoking the service bridge switching on the protection pathaccording to the switching flow of 1:N or M:N protection protocol in theprior art, and restoring the service carried on the protection path.

202, restoring the service priority of the protection path to its fixedpriority at the failure point and the distal end of the failure point bytransmitting a protocol message in the protection path.

203, the failure point detecting whether there are other failed servicepaths for which service bridge switching is not performed yet, if yes,selecting the service path with the highest service priority therefrom,and carrying out protection of the failed service path with the highestservice priority according to the steps described in the firstembodiment.

204, end.

Utility of the service paths is increased in the second preferredembodiment of the present invention, thereby making the linearprotection method for the optical network more effective.

After the protection action is carried out among the service paths ofthe optical network for many times, it is possible that the service pathwith a higher fixed priority is used for protection while the servicepath with a lower fixed priority works normally. According to a thirdpreferred embodiment of the present invention, a process of protectionpath adjustment is added after the first preferred embodiment or thesecond preferred embodiment to adjust the non-protection path to aservice path with a high fixed priority so that the service having ahigher service priority on the service path with a higher fixed prioritycan be implemented in time.

301, seeking a service path having the highest fixed priority from allthe protection paths, and if it is found, proceeding to step 302,otherwise, proceeding to step 307.

302, finding out a non-protection path having the lowest servicepriority from all the non-protection paths.

303, comparing the fixed priority of the protection path with theservice priority of the non-protection path, if the former one is higherthan the latter one, then proceeding to step 304, otherwise, proceedingto step 307.

304, revoking the service bridge switching on the protection path havingthe highest fixed priority according to the service bridge switchingflow of 1:N or M:N protection protocol in the prior art, and modifyingits service priority to be its fixed priority.

305, bridge switching the service on the protection path having thehighest fixed priority to the non-protection path having the lowestservice priority according to the service bridge switching flow of 1:Nor M:N protection protocol in the prior art; and modifying the servicepriority of the non-protection path having the lowest service priority,the modified service priority being the service priority of theprotection path having the highest fixed priority.

306, returning to step 301.

307, end.

The third embodiment may be executed automatically after the firstembodiment or the second embodiment, or may be manually initiated forexecution as desired.

The seven service paths between a first node and a second node in a SDHnetwork serve as a linear protection group to implement the protectionmethod of the present invention through the following steps:

The initial states of the seven service paths are all normal workingstate, a corresponding fixed priority is configured for each servicepath, the fixed priorities of the seven service paths deceaseprogressively from one to seven according to the sequencing of theservice paths, and the service priorities of the services carried on theseven service paths are equal to the fixed priorities when there is noservice bridge switching among the seven service paths. In other words,the fixed priority of the first service path is one, and when there isno service bridge switching, the service priority of the service carriedon the first service path is also one; the fixed priority of the secondservice path is two, and when there is no service bridge switching, theservice priority of the service carried on the second service path isalso two, and so forth, till the seventh service path, as shown inFIG. 1. In the seven service paths, default codes without request, i.e.,the NRm,n protocol messages in the drawings, are sent through protocolbytes, wherein the NRm,n protocol message is a message defined in theSDH or OTN protection protocol.

The first node detects a failure in the second service path, as shown inFIG. 2, in which the service path having a failure is indicated by across. In the present invention, in an optical network, the node wherethe seven service paths are located is noted as a first node, i.e., thefailure point; the node of the other end in the optical networkcorresponding to the first node is noted as a second node, i.e., thedistal end of the failure point. The present invention implementsservice bridge switching for the second service path having a failure soas to protect it according to the following steps of:

401, the first node seeking a protection path for the second servicepath from the service paths with service priorities lower than that ofthe second service path, wherein the protection path is the service pathwith the lowest service priority, i.e., the seventh service path.

402, the first node and the second node bridge switching the service onthe second service path to the seventh service path based on negotiationthrough service bridge switching protocol messages, as shown in FIG. 2.

Both the SRm,n and the RRm,n in FIG. 2 are identical to theircounterparts defined in the SDH or OTN protocol.

403, the first node and the second node modifying the service priorityof the seventh service path to be the fixed priority of the secondservice path.

The service priority of the seventh service path used as the protectionpath can be comprehended as the identifier 2 of the message SF2,2 inFIG. 2. The service priority of the protection path in all the drawingsof the embodiments of SDH network in the present invention can becomprehended in a similar way.

404, end.

As shown in FIG. 3, when the first service path, the second servicepath, the third service path and the fourth service path in the SDHnetwork each has a failure, and the fifth service path, the sixthservice path and the seventh service path are used to protect the firstservice path, the second service path and the third service pathrespectively, if the first node detects the restoration of the secondservice path, then the service bridge switching should be revokedaccording to the following steps.

501, revoking the service bridge switching between the second servicepath and the sixth service path, and restoring the service carried onthe sixth service path.

502, the first node and the second node restoring the service priorityof the sixth service path to its fixed priority, as shown in FIG. 4.

503, the first node finding by checking that the fourth service path hasa failure and no service bridge switching is performed for it yet, thenbridge switching the service on the fourth service path to the sixthservice path according to the steps 401 to 404, as shown in FIG. 5.

504, end.

The initial state of the SDH network includes the service bridgeswitching from the first service path to the seventh service path, theservice bridge switching from the fourth service path to the sixthservice path, and the service bridge switching from the third servicepath to the fifth service path, and afterwards, the first service pathis restored, accordingly only the service bridge switching from thefourth service path to the sixth service path and the service bridgeswitching from the third service path to the fifth service path remains.At this time, the fifth service path and the sixth service path are usedfor protection, and their priorities are both higher than that of theseventh service path which is working normally, as shown in FIG. 6. Insuch case, the fifth service path and the sixth service path areadjusted according to the following steps.

601, finding out a protection path with the highest fixed priority,i.e., finding the fifth service path which is the protection path withthe highest fixed priority from the fifth service path and the sixthservice path.

602, finding out a non-protection path with the lowest service priority,i.e., finding the seventh service path which is the non-protection pathwith the lowest service priority from all the non-protection paths.

603, the fixed priority of the fifth service path being higher than theservice priority of the seventh service path.

604, as shown in FIG. 7, revoking the service bridge switching from thethird service path to the fifth service path, and restoring the servicepriority of the fifth service path to its fixed priority.

605, bridge switching the service on the third service path to theseventh service path, and modifying the service priority of the seventhservice path to be the service priority of the third service path, asshown in FIG. 8.

606, repeating step 601, and the sixth service path being the protectionpath with the highest fixed priority; repeating step 602, and the fifthservice path being the non-protection path with the lowest servicepriority; then learning by comparison that the fixed priority of thesixth service path is not higher than the service priority of the fifthservice path.

607, end.

The linear protection method for an optical network provided by thepresent invention is irrelevant with the level of a network to belinearly protected, and can be used for linear protection of SDHmultiplex section layer, protection of SDH higher order path or lowerorder path layer, and linear protection of ODU path layer of OTN. Thepresent invention utilizes overhead bytes in an optical network totransmit information: in regard to the linear protection of SDHmultiplex section layer, K1, K2 bytes may be used to transmit protocolmessages; in regard to the linear protection of SDH higher order path orlower order path layer, K3, K4 bytes may be used to transmit protocolmessages; and in regard to the linear protection of ODU path layer ofOTN, the APS byte of the ODU layer may be used to transmit protocolmessages.

It shall be appreciated that the above detailed description of thepreferred embodiments of the present invention should not be regarded aslimitations to the protection scope of the present patent of invention,which is defined by the attached claims.

INDUSTRIAL APPLICABILITY

The present invention provides a linear protection method for an opticalnetwork, in which the services carried on a group of service paths thatparticipate in the linear protection of the optical network areclassified into different service priorities, and overhead bytes in theoptical network are utilized to transmit information, so as to achievethe function of automatically seeking a service path having a lowservice priority when any one of the service paths has a failure, toprotect the failed service path, thereby increasing the flexibility ofconfiguring protection manners and the security of services in theoptical network and enhancing the operability in application as well.

What I claim is:
 1. A linear protection method for an optical network,used for protecting a failed service path in the optical network, themethod comprising the following steps of: A. setting a priority ofservice carried on each service paths participating in linear protectionof the optical network as a service priority for each service path; andB. selecting, from service paths participating in the linear protection,a service path of which the service priority is lower than that of thefailed service path as a protection path, and bridge switching theservice on the failed service path to the protection path; wherein thestep B comprises: selecting, from the service paths participating in thelinear protection, a service path, of which the service priority islower than that of the failed service path and meanwhile is the lowest,as the protection path, bridge switching the service on the failedservice path to the protection path, and modifying the service priorityof the protection path to be the service priority of the failed servicepath; and the method further comprising: if there are a plurality ofservice paths of which the service priorities are lower than that of thefailed service path and meanwhile are the lowest, then selectingtherefrom a service path which is a non-protection path as theprotection path of the failed service path.
 2. The protection methodaccording to claim 1, further comprising the following step before thestep B: configuring a fixed priority for each service pathsparticipating in the linear protection of the optical network andsetting the service priority of each service path to be equal to thefixed priority.
 3. The protection method according to claim 2, whereinthe step B further comprises a process of restoring the protection pathback to the service path after the failed service path is recovered,which comprises the following steps of: C1. revoking existing servicebridge switching on the protection path corresponding to the failedservice path, and restoring the service carried on the protection path;and C2. restoring a protection priority of the protection pathcorresponding to the failed service path to the service prioritythereof.
 4. The protection method according to claim 3, furthercomprising the following step after the step C2: the failure pointdetecting whether there are other failed service paths for which servicebridge switching is not performed yet, if yes, finding out a servicepath with the highest service priority therefrom in order to protect thefailed service path with the highest service priority.
 5. The protectionmethod according to claim 2, wherein the step B further comprises aprocess of protection path adjustment, which comprises the followingsteps of: D1. selecting a protection path with the highest fixedpriority; D2. selecting a non-protection path with the lowest servicepriority; D3. comparing the fixed priority of the protection path withthe service priority of the non-protection path; if the former one ishigher than the latter one, revoking the service bridge switching on theprotection path with the highest fixed priority, restoring the servicepriority of the protection path with the highest fixed priority to thefixed priority thereof, and using the non-protection path with thelowest service priority as a new protection path; and D4. setting up theservice bridge switching previously on the protection path with thehighest fixed priority on the non-protection path with the lowestservice priority, and modifying the service priority of thenon-protection path with the lowest service priority to be the servicepriority of the protection path with the highest fixed priority.
 6. Theprotection method according to claim 1, further comprising: setting anode where the failed service path is located in the optical network asa failure point, which selects the protection path for the failedservice path in the step B.
 7. The protection method according to claim1, further comprising: if the service path, of which the servicepriority is lower than that of the failed service path and meanwhile isthe lowest, is already a protection path, then revoking existing servicebridge switching on the protection path, and then bridge switching theservice on the failed service path to the protection path.
 8. Theprotection method according to claim 7, further comprising: if there area plurality of service paths of which the service priorities are lowerthan that of the failed service path and meanwhile are the lowest, butall of the plurality of service paths are already protection paths, thenselecting therefrom a protection path with the lowest fixed priority asthe protection path of the failed service path.